The practise of feeding birds, particularly during winter months, is well established and practised in many different countries. Typically, bird feeders are utilized to entice birds to feed thereat. Many people enjoy the sight of birds feeding and try to attract different types of birds. Some birds, particularly song birds, are considered very desirable.
However, there are certain other birds, typically some of the larger birds, which are not considered desirable. These birds will typically consume a lot of feed and many are not considered attractive. Typical of such birds would be pigeons, starlings, grackles, etc. However, the problem of excluding such birds remains.